In power and energy systems, both the aerodynamic performance and the structure reliability of turbine equipment are affected by utilized blades. In general, the design process of blade is high ...dimensional and nonlinear. Different coupled disciplines are also involved during this process. Moreover, unavoidable uncertainties are transported and accumulated between these coupled disciplines, which may cause turbine equipment to be unsafe. In this study, a saddlepoint approximation reliability analysis method is introduced and combined with collaborative optimization method to address the above challenge. During the above reliability analysis and design optimization process, surrogate models are utilized to alleviate the computational burden for uncertainties‐based multidisciplinary design and optimization problems. Smooth response surfaces of the performance of turbine blades are constructed instead of expensively time‐consuming simulations. A turbine blade design problem is solved here to validate the effectiveness and show the utilization of the given approach.
Metal‐based materials with exceptional intrinsic conductivity own excellent electromagnetic interference (EMI) shielding performance. However, high density, corrosion susceptibility, and poor ...flexibility of the metal severely restrict their further applications in the areas of aircraft/aerospace, portable and wearable smart electronics. Herein, a lightweight, flexible, and anticorrosive silver nanowire wrapped carbon hybrid sponge (Ag@C) is fabricated and employed as ultrahigh efficiency EMI shielding material. The interconnected Ag@C hybrid sponges provide an effective way for electron transport, leading to a remarkable conductivity of 363.1 S m−1 and superb EMI shielding effectiveness of around 70.1 dB in the frequency range of 8.2–18 GHz, while the density is as low as 0.00382 g cm−3, which are among the best performances for electrically conductive sponges/aerogels/foams by far. More importantly, the Ag@C sponge surprisingly exhibits super‐hydrophobicity and strong corrosion resistance. In addition, the hybrid sponges possess excellent mechanical resilience even with a large strain (90% reversible compressibility) and an outstanding cycling stability, which is far better than the bare metallic aerogels, such as silver nanowire aerogels and copper nanowire foams. This strategy provides a facile methodology to fabricate lightweight, flexible, and anticorrosive metal‐based sponge for highly efficient EMI shielding applications.
Anticorrosive, ultralightweight, and flexible silver nanowire wrapped with carbon hybrid sponge is designed and employed as electromagnetic interference (EMI) shielding material with ultrahigh efficiency. The interconnected hybrid sponge shows superb EMI shielding effectiveness of 70.1 dB, while the density is as low as 0.00382 g cm−3, which are among the best performances for electrically conductive sponges/aerogels/foams by far.
•A computational-experimental framework for fatigue reliability assessment.•Two schemes based on probabilistic S-N curves and stochastic FE simulations.•Probabilistic plasticity induced stress-strain ...response analysis under uncertainty.•Real case of a bladed disk by combing overspeed testing with stochastic FE analysis.
In the present study, a computational-experimental framework is developed for fatigue reliability assessment of turbine bladed disks. Within the framework, the overspeed testing is innovatively combined with stochastic finite element (FE) analysis for quantifying uncertainties in the experimental data, material properties and loads. Meanwhile, two schemes are elaborated based on probabilistic S-N curves and stochastic FE simulation coupling with sampling technique. The stochastic FE simulation incorporates the Chaboche constitutive model with Fatemi–Socie criterion for fatigue behavior modeling and life prediction. Moreover, experimental deformation and numerical FE analysis are conducted with regard to the full-scale bladed disk test with increased step-stress overloading. Reliability sensitivity analysis is performed to provide an importance ranking of random variables for fatigue design of the bladed disk. Results indicate that stochastic FE analysis-based scheme provides more conservative predictions than the probabilistic S-N curves-based one.
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•A modified generalized local model considering multiaxial stress and stress gradient is developed.•A novel probabilistic framework for notch fatigue analysis considering size effects is ...established.•Probabilistic fatigue life prediction of TA19 notched specimens with different scales are conducted.
Structural integrity assessments with discontinuities are critical for ensuring operational life and reliability of engineering components. In this work, through combining with the generalized local model, a probabilistic framework is proposed for fatigue life assessment of notched components under size effects, in which the Smith–Watson–Topper damage parameter is utilized to characterize the multiaxial stress state at the notch tip. In particular, an effective stress concept is introduced to characterize the inhomogeneous stress distribution within the notch region. Finally, experimental data of TA19 notched specimens with different scales are utilized for model validation and comparison, results show that the proposed framework yields acceptable correlations of predicted fatigue lives with experimental ones.
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•Combined critical plane-critical distance approach for notch fatigue analysis under multiaxial loadings is proposed.•Eight life assessment procedures with different coupling sequence of critical ...plane and TCD concepts are explored.•Procedures using the CPA before the TCD own better predictions than that after the TCD.•Procedures regarding the critical distance as a fatigue lifetime related function provides better correlations than others.
Combinations of geometric discontinuities and multiaxial loads appear commonly in engineering components, which raise both stress gradient and multiaxial stress states near the notch root. This work studies the combined critical plane approach with the theory of critical distance for fatigue analysis of notched components under multiaxial loadings. Taking the Fatemi-Socie model for instance, different coupling sequence of critical plane and critical distance concepts is discussed. In particular, the influence of employing the point method and the line method of the theory of critical distance on predicting performance as well as the rationality of regarding the critical distance as a material constant or as a function related to fatigue life are also investigated. Accordingly, 8 life assessment procedures are summarized and the optimal procedure is determined and verified by experimental data of Al 7050-T7451 and GH4169 alloys. Results show that the majority of the predicted points fall within the ±2 scatter band according to experimental results and the procedures which employ the theory of critical distance after using the critical plane approach and regarding the critical distance as a function related to fatigue life provide better accuracy on fatigue life prediction than others.
Abstract
Electrochemical CO
2
reduction reaction (CO
2
RR) to liquid fuels is currently challenged by low product concentrations, as well as their mixture with traditional liquid electrolytes, such ...as KHCO
3
solution. Here we report an all-solid-state electrochemical CO
2
RR system for continuous generation of high-purity and high-concentration formic acid vapors and solutions. The cathode and anode were separated by a porous solid electrolyte (PSE) layer, where electrochemically generated formate and proton were recombined to form molecular formic acid. The generated formic acid can be efficiently removed in the form of vapors via inert gas stream flowing through the PSE layer. Coupling with a high activity (formate partial current densities ~450 mA cm
−2
), selectivity (maximal Faradaic efficiency ~97%), and stability (100 hours) grain boundary-enriched bismuth catalyst, we demonstrated ultra-high concentrations of pure formic acid solutions (up to nearly 100 wt.%) condensed from generated vapors via flexible tuning of the carrier gas stream.
Circular RNAs (circRNAs) represent a widespread class of non-coding RNAs generated from back-splicing, with a circular loop structure. Many circRNAs have been reported to play essential roles in ...cancer development and have the potential to serve as a novel class of biomarkers for clinical diagnosis. However, the role of circRNA in osteosarcoma (OS) remains largely unknown. In the current study, we examined the expression level of circular RNA PVT1 (circPVT1), previously screened and identified the oncogenic role in gastric cancer, in OS and found that circPVT1 was significantly up-regulated in the OS tissues, serums and chemoresistant cell lines, correlated with poor prognosis of OS patients. Besides, ROC curve demonstrated that circPVT1 may be a better diagnostic biomarker than alkaline phosphatase (ALP) in OS with more sensitivity and specificity. In addition, functional assays revealed that circPVT1 knockdown by siRNA could weaken the resistance to doxorubicin and cisplatin of OS cells through decreasing the expression of classical drug resistance-related gene ABCB1. These findings may provide a new insight into the role of circPVT1 as a biomarker for the diagnosis and treatment target of OS.
Computing the sensitivity vector in the traditional first order reliability method may provide inaccurate reliability outcomes for discrete performance functions and inefficient computation burden ...for high-dimensional problems. In this study, two improved particle swarm optimization algorithms are proposed to enhance the convergence rate with global optimal results during the structural reliability analysis. The abilities for convergence speed and global convergence of the particle swarm optimization algorithm are improved using a novel hybrid method called particle swarm optimization-based harmony search algorithm (PSO–HS), and enhanced particle swarm optimization (EPSO). The proposed methods use a dynamic self-adaptive term to execute the local adjusting process. Using twelve numerical-based engineering problems, the structural reliability frameworks developed based on modified versions of particle swarm optimization algorithms are compared to numerous FORM algorithms and the current metaheuristic methods. Results indicated that the novel proposed methods using the improved PSO algorithms are more robust and efficient than the analytical FORM methods for solving high-dimensional engineering problems. Furthermore, compared to the previous metaheuristic approaches, the suggested methods enabled faster convergence.
•Two optimization algorithms are proposed as novel hybrid FORM in structural reliability analysis.•Local adjusting process is proposed in hybrid FORM methods of EPSO and PSO–HS.•PSO–HS and EPSO compared with PSO, HS, IHS, IPSO, LS-PSO and six FORM algorithms.•Proposed methods are more efficient than FORM for high-dimensional problems.
•Framework for fatigue reliability analysis under multi-source uncertainties.•Manufacturing errors/tolerances are included for fatigue reliability analysis.•Sensitivity analysis of a turbine bladed ...disk is conducted for fatigue design.•Geometrical uncertainty shows critical influences on fatigue reliability.
Turbine bladed disks normally operate under complex loadings coupling with uncertainties originate from multiple sources, including material variability, load variation and geometrical uncertainty. The influence of these uncertainties on mechanical response of engineering components are critical for their fatigue assessment and reliability evaluation. In this work, a general framework for fatigue reliability analysis is developed by coupling the Latin hypercube sampling with FE analysis to describe the combined effects of multi-source uncertainties. Fatigue reliability analysis of a full-scale bladed disk under multi-source uncertainties was performed as well as sensitivity analysis for fatigue design. In order to describe the manufacturing errors or tolerances, random dimensions are inputted. Comparing the predicted fatigue lifetime distributions with/without geometrical uncertainty, it shows that geometrical uncertainty matters in structural fatigue reliability. Particularly, sensitivity analysis indicates that the geometrical uncertainty exerts more critical influences on the fatigue lifetime and reliability of the turbine bladed disk than others. The sensitivity factors of three typical dimensions emerges the influence of designed sizes and dimensional tolerances on the failure probability, which provides a reference for engineering design.
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